Filters having improved permeability and virus removal capabilities

ABSTRACT

A filter block having a permeability of greater than about 3.0*10 −9  cm 2 , and a F-VLR of greater than about 99% is provided. The filter block may be made of filter particles having a median particle size of less than about 50 microns and having a particle span of about 1.4 or less. The filter blocks of the present invention can be used to make a filter for filtering liquids and more specifically, for providing potable water. The filter particles may be mesoporous. Kits comprising filters and information relating to the killing or removal of bacteria, viruses, and microbials are also provided.

FIELD OF THE INVENTION

The present invention relates to the field of filter materials, filtersmade from those materials and, more particularly, to the field of waterfilters.

BACKGROUND OF THE INVENTION

Water may contain many different kinds of contaminants including, forexample, particulates, chemicals, and microbiological organisms, such asbacteria, viruses, and protozoa. In a variety of circumstances, thesecontaminants must be reduced in concentration or completely removedbefore the water can be used. For example, in many medical applicationsand in the manufacture of certain electronic components, extremely purewater is required. As a more common example, any harmful contaminantsmust be removed from the water before it is potable, i.e., fit toconsume.

The quality of water varies widely around the world. In the U.S. andother developed countries, drinking water is typically municipallytreated. During that treatment, contaminants, such as suspended solids,organic matter, heavy metals, chlorine, bacteria, viruses, and protozoaare removed from the water before it is discharged to the homes ofconsumers. However, equipment malfunction and/or infrastructurebreakdown and other problems with water treatment utilities can lead toincomplete removal of the contaminants.

Many developing countries are without water treatment utilities. Assuch, there are deadly consequences associated with exposure tocontaminated water, as many developing countries have increasingpopulation densities, increasingly scarce water resources, and no watertreatment utilities. It is common for sources of drinking water to be inclose proximity to human and animal waste, such that microbiologicalcontamination is a major health concern.

As a result of waterborne microbiological contamination, an estimatedsix million people die each year, half of which are children under 5years of age. In 1987, the U.S. Environmental Protection Agency (herein“EPA”) introduced the “Guide Standard and Protocol for TestingMicrobiological Water Purifiers”. This guide standard and protocolprovides guidelines and performance requirements for drinking watertreatment systems that are designed to reduce specific health relatedcontaminants in public or private water supplies. The requirements arethat the effluent from a water treatment system exhibits 99.99% (orequivalently, 4 log) removal of viruses, 99.9999% (or equivalently, 6log) removal of bacteria, and 99.9% (or equivalently, 3 log) removal ofprotozoa (cysts) against a challenge.

Under the EPA guide standard and protocol, in the case of viruses, theinfluent concentration should be about 1×10⁷ viruses per liter (PFU/L),and in the case of bacteria, the influent concentration should be about1×10⁸ bacteria per liter (CFU/L). Because of the prevalence ofEscherichia coli (E. coli, bacterium) in water supplies, and the risksassociated with its consumption, this microorganism is used as thebacterium in the majority of studies. Similarly, the MS-2 bacteriophage(or simply, MS-2 phage) is typically used as the representativemicroorganism for virus removal because its size and shape (i.e., about26 nm and icosahedral) are similar to many viruses. Thus, a filter'sability to remove MS-2 bacteriophage demonstrates its ability to removeother viruses.

It was believed by those skilled in the relevant art that smallsuspended particles, for example, bacteria and viruses, are bestfiltered by filters having small interstitial spacing between filterparticles. Small space between filter particles is best achieved byclose packing of the filter particles. One way to achieve close packingis described in published PCT application WO 00/71467 A1, in the name ofTremblay et al., which teaches the use of small particles to fill in thespaces between larger particles. This provides close packing by usingfilter particles having a bi-modal size distribution. Moreover, U.S.Pat. Nos. 5,922,803 and 6,368,504 B1, issued to Koslow et al. andKuennen et al., respectively, teach the general principle of usingfilter particles having a narrow particle size distribution, that is,particles that are generally all the same size, to insure that theinterstitial spacing between particles is relatively uniform. Theaverage particle size of these two narrow particle size distributionpatents ranges from 80 μm to 45 μm. These patents describe filters thatachieve either a relatively high level of virus removal with a highpressure drop across the filter or low virus removal since the averagefilter particle size is relatively large although the size distributionis narrow.

A high pressure drop across a filter can cause reduced flow and otherproblems that are viewed negatively by filter users. Going to smallerparticle sizes, for example, less than 45 μm was believed to furtherexacerbate the pressure drop across a filter. Moreover, those skilled inthe art will appreciate that the pressure drop has a direct impact onflow rate through a filter block. Consumers typically have waterdelivered to their homes at a fixed pressure (from the municipality orfrom a pump in their well, for example). Thus a filter block with a highpressure drop will have a slower flow rate than one with a smallerpressure drop. As can be appreciated, consumers do not like to wait longperiods of time for their water, so high flow rates are preferred. Assuch, filter blocks with low pressure drops are necessarily preferred byconsumers. Thus, there exists a need for filters, processes formanufacturing filter materials and filter materials which are capable ofremoving bacteria and/or viruses from a fluid without thedisadvantageous increase in pressure drop exhibited by filters of theprior art.

SUMMARY OF THE INVENTION

In one aspect of the present invention there is provided a filter blockhaving a permeability of greater than about 3.0×10⁻⁹ cm², and a F-VLR ofgreater than about 99%. Preferably the permeability is greater thanabout 3.5×10⁻⁹ cm², more preferably greater than about 4.0×10⁻⁹ cm² evenmore preferably greater than about 4.5×10⁻⁹ cm² and most preferablygreater than about 5.0×10⁻⁹ cm². Preferably, the F-VLR is greater thanabout 99.9%, more preferably greater than about 99.99%, and even morepreferably greater than about 99.999%, and most preferably greater thanabout 99.9999%. Additionally, it is preferred that the filter blocks ofthe present invention have a F-BLR of greater than about 99.99%,preferably greater than about 99.999%, and more preferably greater thanabout 99.9999%.

In another aspect of the present invention the preferred filterpermeability is obtained by making the filter block from filterparticles having a median particle size of less than about 50 μm,preferably less than about 40 μm, more preferably less than about 37.5μm, and even more preferably less than about 35 μm. In yet anotheraspect of the present invention the filter particles have a particlespan of about 1.8 or less, preferably 1.5 or less, more preferably 1.4or less, and even more preferably 1.3 or less.

It has been surprising determined that filter permeability is animportant parameter for regulating the pressure drop across a filterwhile simultaneously improving the removal of small suspended particlessuch as bacteria and viruses. As discussed above, it was generallybelieved that improvements in the removal of small suspended particlescame only at the expense of a filter's flow properties. The presentinvention proves that this is not the case, and as such, provides asubstantial benefit over the teachings of the prior art. Morespecifically, the present invention provides the manufacturers anddesigners of filters a filter parameter that optimizes the removal ofsmall suspended particles with little or no reduction in filter flowcharacteristics. Methods of making filters, and filter materials usedtherein are also taught.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of flow through a radial filterblock;

FIG. 2 is a schematic representation of flow through an axial filterblock; and

FIG. 3 is a schematic representation of a pressure/flow control devicesuitable for use with the filters of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

All documents cited are, in relevant part, incorporated herein byreference. The citation of any document is not to be construed as anadmission that it is prior art with respect to the present invention.

I. Definitions

As used herein, the terms “filters” and “filtration” refer to structuresand mechanisms, respectively, associated with microorganism removal(and/or other contaminant removal), via primarily adsorption and/or sizeexclusion to a lesser extent.

As used herein, the phrase “filter material” is intended to refer to anaggregate of filter particles. The aggregate of the filter particlesforming a filter material can be either homogeneous or heterogeneous.The filter particles can be uniformly or non-uniformly distributed(e.g., layers of different filter particles) within the filter material.The filter particles forming a filter material also need not beidentical in shape or size and may be provided in either a loose orinterconnected form. For example, a filter material might comprisemesoporous and basic activated carbon particles in combination withactivated carbon fibers, and these filter particles may be eitherprovided in loose association or partially or wholly bonded by apolymeric binder or other means to form an integral structure.

As used herein, the phrase “filter particle” is intended to refer to anindividual member or piece, which is used to form at least part of afilter material. For example, a fiber, a granule, a bead, etc. are eachconsidered filter particles herein. Further, the filter particles canvary in size, from impalpable filter particles (e.g., a very finepowder) to palpable filter particles.

As used herein, the phrase “filter block” is intended to refer to amixture of filter particles bound together to form a structure that iscapable of filtering a liquid, for example water, air, hydrocarbons, andthe like. As such a filter block may comprise filter particles, binderparticles, and other particles or fibers for the removal of specificcontaminants, such as lead, mercury, arsenic, etc. A filter block canvary in geometry and flow patterns. Examples of radial flow and axialflow filter blocks are described herein (see for example, FIGS. 1 and2), but other filter configurations, for example plate and conical, willbe known to those skilled in the art. The examples given herein areillustrative only and are not intended to limit the present invention.Often, but not always, the filter block is encased in a “filter housing”which protects the filter block from damage and provides seals betweenthe “dirty” liquid being filtered and the “clean” liquid leaving thefilter as the desired product. While these sealing surfaces may bepermanently attached to, or integral with the filter block, andnecessary to separate the clean liquid from the dirty liquid, they arenot considered part of the filter block for purposes of the calculationsherein.

As used herein, the phrase “median particle size” refers to the diameterof a particle below or above which 50% of the total volume of particleslies. This median particle size is designated as D_(v,0.50). While manymethods and machines are known to those skilled in the art forfractionating particles into discreet sizes, sieving is one of theeasiest, least expensive and common ways to measure particle sizes andparticle size distributions. An alternative preferred method fordetermining size distribution of particles is with light scattering.Further, the phrase, “particle span” is a statistical representation ofa given particle sample and can be calculated as follows. First, themedian particle size, D_(v,0.50), is calculated as described above. Thenby a similar method, the particle size that separates the particlesample at the 10% by volume fraction, D_(v,0.10′) is determined, andthen the particle size that separates the particle sample at the 90% byvolume fraction, D_(v,0.90′) is determined. The particle span is thenequal to: (D_(v,0.90)−D_(v,0.10))/D_(v,0.50).

As used herein, the phrase “filter block pore volume” refers to thetotal volume of the inter-particle pores (also called interstitialspacings) in the filter block with sizes larger than 0.1 μm.

As used herein, the phrase “filter block volume” refers to the sum ofthe filter block pore volume and the volume occupied by the filterparticles. That is, the filter block volume is the total volume of thefilter block calculated based on the external dimensions of the filterblock. For example, in FIG. 1, the filter block volume is calculated as:πL_(r)(r₂ ²−r₁ ²), and in FIG. 2, the filter block volume is calculatedas: πL_(a)r_(a) ². The units used herein are generally cm, but thoseskilled in the art will recognize that any appropriate units of lengthcan be used for L and r.

As used herein, the terms “microorganism”, “microbiological organism”,“microbial”, and “pathogen” are used interchangeably. These terms referto various types of microorganisms that can be characterized asbacteria, viruses, parasites, protozoa, and germs.

As used herein, the phrase “Filter Bacteria Log Removal (F-BLR)” refersto the bacteria removal capability of the filter after the volumetricflow of liquid is equal to at least 10 filter block volumes and theliquid flow rate through the filter block is equal at least 600 mL/min.The F-BLR is defined and calculated as:F-BLR=−log [(effluent concentration of E. coli)/(influent concentrationof E. coli)],where the “influent concentration of E. coli” is set to about 1×10⁸CFU/L continuously throughout the test and the “effluent concentrationof E. coli” is measured after the volumetric flow of liquid through thefilter block is equal to at least 10 filter block volumes. F-BLR hasunits of “log” (where “log” is the logarithm). Note that if the effluentconcentration is below the limit of detection of the technique used toassay, then the effluent concentration for the calculation of the F-BLRis considered to be the limit of detection. Also, note that the F-BLR ismeasured without application of chemical agents that providebactericidal effects.

As used herein, the phrase “Filter Viruses Log Removal (F-VLR)” refersto the viruses removal capability of the filter after the volumetricflow of liquid is equal to at least 10 filter block volumes and theliquid flow rate through the filter block is equal at least 600 mL/min.The F-VLR is defined and calculated as:F-VLR=−log [(effluent concentration of MS-2)/(influent concentration ofMS-2)],where the “influent concentration of MS-2” is set to about 1×10⁷ PFU/Lcontinuously throughout the test and the “effluent concentration ofMS-2” is measured after the volumetric flow of liquid through the filterblock is equal to at least 10 filter block volumes. F-VLR has units of“log” (where “log” is the logarithm). Note that if the effluentconcentration is below the limit of detection of the technique used toassay, then the effluent concentration for the calculation of the F-VLRis considered to be the limit of detection. Also, note that the F-VLR ismeasured without application of chemical agents that provide virucidaleffects.

As used herein, the term “micropore” is intended to refer to anintra-particle pore having a width or diameter less than 2 nm (orequivalently, 20 Å).

As used herein, the term “mesopore” is intended to refer to anintra-particle pore having a width or diameter between 2 nm and 50 μm(or equivalently, between 20 Å and 500 Å).

As used herein, the term “macropore” is intended to refer to anintra-particle pore having a width or diameter greater than 50 nm (orequivalently, 500 Å).

As used herein, the phrase “total pore volume” and its derivatives areintended to refer to the volume of all the intra-particle pores, i.e.,micropores, mesopores, and macropores. The total pore volume iscalculated as the volume of nitrogen adsorbed at a relative pressure of0.9814 using the BET process (ASTM D 4820-99 standard), a process wellknown in the art.

As used herein, the phrase “micropore volume” and its derivatives areintended to refer to the volume of all micropores. The micropore volumeis calculated from the volume of nitrogen adsorbed at a relativepressure of 0.15 using the BET process (ASTM D 4820-99 standard), aprocess well known in the art.

As used herein, the phrase “sum of the mesopore and macropore volumes”and its derivatives are intended to refer to the volume of all mesoporesand macropores. The sum of the mesopore and macropore volumes is equalto the difference between the total pore volume and micropore volume, orequivalently, is calculated from the difference between the volumes ofnitrogen adsorbed at relative pressures of 0.9814 and 0.15 using the BETprocess (ASTM D 4820-99 standard), a process well known in the art.

As used herein, the phrase “pore size distribution in the mesoporerange” is intended to refer to the distribution of the pore size ascalculated by the Barrett, Joyner, and Halenda (BJH) process, a processwell known in the art.

As used herein, the term “carbonization” and its derivatives areintended to refer to a process in which the non-carbon atoms in acarbonaceous substance are reduced.

As used herein, the term “activation” and its derivatives are intendedto refer to a process in which a carbonized substance is rendered moreporous.

As used herein, the term “activated carbon particles” or “activatedcarbon filter particles” and their derivatives are intended to refer tocarbon particles that have been subjected to an activation process.

As used herein, the phrase “mesoporous activated carbon filter particle”refers to an activated carbon filter particle wherein the sum of themesopore and macropore volumes may be greater than 0.12 mL/g.

As used herein, the phrase “microporous activated carbon filterparticle” refers to an activated carbon filter particle wherein the sumof the mesopore and macropore volumes may be less than 0.12 mL/g.

As used herein, the phrase “mesoporous and basic activated carbon filterparticle” is intended to refer to an activated carbon filter particlewherein the sum of the mesopore and macropore volumes may be greaterthan 0.12 mL/g and has a point of zero charge greater than 7.

As used herein, the phrase “axial flow” refers to flow through a planarsurface and perpendicularly to that surface.

As used herein, the phrase “radial flow” typically refers to flowthrough essentially cylindrical or essentially conical surfaces andperpendicularly to those surfaces.

As used herein, the phrase “face area” refers to the area of the filtermaterial initially exposed to the influent water. For example, in thecase of axial flow filters, the face area is the cross sectional area ofthe filter material at the entrance of the fluid, and in the case of theradial flow filter, the face area is the outside area of the filtermaterial.

II. Permeability

It has unexpectedly been determined that a key parameter for filterblock design is the filter's permeability. As discussed above, priorattempts to make filter blocks that remove small, that is, sub-micronsuspended particles, resulted in filter blocks with poor flowcharacteristics, and more specifically, high pressure drops across thefilter blocks. It turns out that these prior filter blocks have lowpermeability, see for example, Table 1 in the Example section herein.

Permeability is an intrinsic property of a filter block that can becalculated for a given flow rate, pressure drop across the filter block,viscosity of the filtered fluid and the general geometric measurementsof the filter block. The following two formulae can be used to calculatethe permeability for radial and axial flow filter blocks, which areamong the most commonly used filter blocks, and the preferredconfiguration of the filter blocks disclosed herein. Those skilled inthe art will easily be able to adapt these formulae to other filterblock geometries. The permeability of a radial flow filter block iscalculated as:

${\kappa_{r} = {\frac{\mu}{2\pi}\frac{\ln\left( {r_{2}/r_{1}} \right)}{L_{r}}\frac{Q_{r}}{\Delta\; P_{r}}}},$and the permeability of an axial flow filter block is calculated as:

${\kappa_{a} = {\frac{\mu}{\pi}\frac{L_{a}}{r_{a}^{2}}\frac{Q_{a}}{\Delta\; P_{a}}}},$wherein: Q_(r) is the radial flow rate, Q_(a) is the axial flow rate (inmL/s, or cm³/s), μ is the viscosity (in poise or dynes-s/cm²), ln is thenatural log, r_(a) is the radius of an axial flow filter, r₂ is theoutside radius of a radial flow filter, r₁ is the inside radius of aradial flow filter (all in cm), ΔP_(r) is the pressure drop of a radialflow filter, ΔP_(a) is the pressure drop of an axial flow filter (indynes/cm²), L_(r) is the length of a radial flow filter, and L_(a) isthe length of an axial flow filter (in cm).

Turning now to FIG. 1, which is a schematic representation of a radialflow filter block 10 according to the present invention, the inlet, or“dirty” flow 12, designated as Q_(r), is shown entering the exteriorsurface area 14, which has an exterior or outside radius 15 designatedas r₂. Flow 12 travels through filter block 10 to interior hollow core16 which has an interior radius 17 designated as r₁. The filtered, or“clean” flow 18 then flows downward through hollow core 16 into acollection vessel (not shown). Filter block 10 has a length 11,designated as L_(r).

Turning now to FIG. 2, which is a schematic representation of an axialflow filter block 20 according to the present invention, the inlet, or“dirty” flow, 22, designated as Q_(a), is shown entering the topsurface, or face area, 24, which has a radius 25 designated as r_(a).Flow 22 travels through filter block 20 to the bottom surface 26. Thefiltered, or “clean” flow 28 then flows into a collection vessel (notshown). Filter block 20 has a length 21, designated as L_(a). Theexterior surface area 13 of an axial filter block 20 is typically sealedso that the liquid being filtered must travel the entire axial length offilter block 20.

In a preferred aspect of the present invention, the outside radius ofthe filter block, that is, either r_(a) or r₂ is less than about 10 cm,preferably less than about 7.5 cm, and more preferably less than about 5cm. Moreover it is preferred that the filter block volume is less thanabout 2000 mL, preferably less than about 1000 mL, more preferably lessthan about 200 mL, more preferably less than about 100 mL, and even morepreferably less than about 50 mL. Those skilled in the art willappreciate that the volume of a radial filter block excludes the volumeof the hollow core.

III. Filter Particles

Preferred filter particles for use in the present invention are carbonparticles, more preferred are activated carbon particles, and even morepreferred are mesoporous activated carbon particles. For a detaileddescription and further definition of mesoporous activated carbon filterparticles see the following printed publications and co-pending patentapplications: PCT applications U.S. Ser. No. 02/27000, U.S. Ser. No.02/27002, U.S. Ser. No. 03/05416, U.S.03/05409, U.S. patent applicationSer. Nos. 10/464,210, 10/464,209, 10/705,572, and 10/705,174, all filedin the name of Mitchell et al. and all assigned to the Procter & GambleCo. All of the aforementioned applications are incorporated herein byreference in their entirety.

Unexpectedly it has been found that mesoporous activated carbon filterparticles adsorb a larger number of microorganisms compared tomicroporous activated carbon filter particles. Also, unexpectedly it hasbeen found that mesoporous and basic activated carbon filter particlesadsorb a larger number of microorganisms compared to that adsorbed bymesoporous and acidic activated carbon filter particles. Furthermore, ithas been found unexpectedly that mesoporous, basic, and reduced-oxygenactivated carbon filter particles adsorb a larger number ofmicroorganisms compared to that adsorbed by mesoporous and basicactivated carbon filter particles without reduced bulk oxygen percentageby weight.

Those skilled in the art will appreciate that filter particles suitablefor use in the present invention include the preferred particles listeddirectly above, as well as other materials selected from the groupconsisting of activated carbon powders, activated carbon granules,activated carbon fibers, zeolites, activated alumina, activatedmagnesia, diatomaceous earth, silver particles, activated silica,hydrotalcites, glass, polyethylene fibers, polypropylene fibers,ethylene maleic anhydride copolymers fibers, sand, clay and mixturesthereof.

One preferred method, but by no means the only method of achieving thedesired permeability for the filter blocks of the present invention, isby manipulating the median particle size and decreasing the particlespan of the filter particles. Specifically, the preferred permeabilitycan be obtained by making the filter block from filter particles havinga median particle size of less than about 50 μm, preferably less thanabout 40 μm, more preferably less than about 37.5 μm and even morepreferably less than about 35 μm. Moreover, it is also preferred thatthe filter particles have a particle span of about 1.8 or less,preferably 1.5 or less, more preferably 1.4 or less, and even morepreferably 1.3 or less.

As described herein the filter blocks of the present invention generallycomprise filter particles and a binder. In one preferred aspect of thepresent invention at least about 50%, preferably at least about 60%,more preferably at least about 70%, and even more preferably at leastabout 80%, by weight, of the filter particles are activated carbonparticles. Those skilled in the art will appreciate that activatedcarbon particles do not include activated carbon fibers, while both aresubsets of the broader category of filter particles. The distinctionbetween fibers and particles is best made by the aspect ratio, that is,a filter particle that has an aspect ratio of greater than about 4:1 isgenerally classified as a fiber, while a filter particle with an aspectratio of about 4:1 or less is generally considered a particle.

IV. Coated Filter Particles

The filter particles used to make the filter blocks and filters of thepresent invention can be coated with a variety of materials that providecertain benefits. For example, the Mitchell et al. U.S. application Ser.Nos. 10/705,572, and 10/705,174 teach a variety of metal and cationiccoatings suitable for use in the present invention. These coatingsprovide viruses and bacteria removal benefits.

When coated filter particles are used, preferably at least a portion ofthe filter particles is coated with a material selected from the groupconsisting of silver, a silver-containing material, a cationic polymerand mixtures thereof. Preferred cationic polymers for use in the presentinvention are selected from the group consisting of:poly(N-methylvinylamine), polyallylamine, polyallyldimethylamine,polydiallylmethylamine, polydiallyldimethylammonium chloride,polyvinylpyridinium chloride, poly(2-vinylpyridine),poly(4-vinylpyridine), polyvinylimidazole, poly(4-aminomethylstyrene),poly(4-aminostyrene),polyvinyl(acrylamide-co-dimethylaminopropylacrylamide),polyvinyl(acrylamide-co-dimethyaminoethylmethacrylate),polyethyleneimine, polylysine, DAB-Am and PAMAM dendrimers,polyaminoamides, polyhexamethylenebiguandide,polydimethylamine-epichlorohydrine, aminopropyltriethoxysilane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride,bis(trimethoxysilylpropyl)amine, chitosan, grafted starch, the productof alkylation of polyethyleneimine by methylchloride, the product ofalkylation of polyaminoamides with epichlorohydrine, cationicpolyacrylamide with cationic monomers, dimethyl aminoethyl acrylatemethyl chloride (AETAC), dimethyl aminoethyl methacrylate methylchloride (METAC), acrylamidopropyl trimethyl ammonium chloride (APTAC),methacryl amodopropyl trimethyl ammonium chloride (MAPTAC), diallyldimethyl ammonium chloride (DADMAC), ionenes, silanes and mixturesthereof. Preferably the cationic polymers are selected from the groupconsisting of: polyaminoamides, polyethyleneimine, polyvinylamine,polydiallyldimethylammonium chloride, polydimethylamine-epichlorohydrin,polyhexamethylenebiguanide, poly-[2-(2-ethoxy)-ethoxyethlyl-guanidinium]chloride.

In addition to the coatings described above that can assist in theremoval or killing of viruses and bacteria, coatings may also be addedto improve the flow characteristics of a filter block thus affecting thepermeability of the filter blocks. For example, drag reducing polymerscan be applied to the filter block to reduce the pressure drop acrossthe filter block. Non limiting examples of drag reducing polymersinclude linear polymers such as polyvinylamine, polyvinylalcohol,polyacrylamide, partially hydrolyzed polyacrylamide, andpolyethyleneoxide. Other examples will be known to those skilled in theart.

V. Filters of the Present Invention

Examples of filter configurations, potable water devices, consumerappliances, and other water filtration devices suitable for use with thepresent invention are disclosed in U.S. Pat. Nos. 5,527,451; 5,536,394;5,709,794; 5,882,507; 6,103,114; 4,969,996; 5,431,813; 6,214,224;5,957,034; 6,145,670; 6,120,685; and 6,241,899, the substances of whichare incorporated herein by reference. Additionally, the patents andapplications referenced above and incorporated herein by reference teachfilters that may be acceptable for use with the present invention. Onepreferred method of making filter blocks of the present invention isdescribed below in the Example section.

In addition to the filter blocks disclosed herein, the filters of thepresent invention may also comprise other filter systems includingreverse osmosis systems, ultra-violet light systems, ozone systems, ionexchange systems, electrolyzed water systems, and other water treatmentsystems known to those with skill in the art. Also, the filters of thepresent invention may comprise pre-filters wrapped around the filterblocks to prevent the filter blocks from clogging with suspendedparticles. Furthermore, the filters of the present invention maycomprise indicator systems and/or shut-off systems to indicate to theconsumer the remaining life/capacity of the filter and to shut-off thefilter when the filter's remaining life/capacity is zero.

As previously discussed, the filter material can be provided in either aloose or interconnected form (e.g., partially or wholly bonded by apolymeric binder or other means to form an integral structure).

The filter material may be used for different applications (e.g., use asa pre-filter or post-filter) by varying the size, shape, complexformations, charge, porosity, surface structure, functional groups, etc.of the filter particles as discussed above. The filter material may alsobe mixed with other materials, as just described, to suit it for aparticular use. Regardless of whether the filter material is mixed withother materials, it may be used as a loose bed, a block (including aco-extruded block as described in U.S. Pat. No. 5,679,248, which isherein incorporated by reference), and mixtures thereof. Preferredmethods that might be used with the filter material include forming ablock filter made by ceramic-carbon mix (wherein the binding comes fromthe firing of the ceramic), using powder between non-wovens as describedin U.S. Pat. No. 6,077,588, which is herein incorporated by reference,using the green strength method as described in U.S. Pat. No. 5,928,588,which is herein incorporated by reference, activating the resin binderthat forms the block, which is herein incorporated by reference, or byusing a resistive heating method as described in PCT Application SerialNo. WO 98/43796. The filter blocks of the present invention can be madeby standard extrusion processes known to those skilled in the art. Suchprocesses are described in U.S. Pat. No. 5,331,037 to Koslow et al.,which is incorporated herein by reference.

The flow rate in a high permeability filter system can be controlledwith a flow or pressure control device. Pressure/flow control devicesinclude pressure regulators that control the input pressure or thepressure drop across the filter. Direct flow control devices create avariable pressure drop dependant on flow rate. The most common flowcontrol device is a flow washer, for example, 30 as shown in FIG. 3.Flow washer 30 is typically a thick elastomeric washer 31 with anorifice 32 in the center. Flow washer 30 is supported at its perimeter33 and deflects into a concave shape in response to inlet flow 34. Thegreater the flow rate the greater the deflection. When flow washer 30deflects it causes the upstream surface of the orifice 35 to decrease insize (increase in pressure drop) thereby controlling the outlet flowrate 36.

VI. Filter Block Examples

Filter blocks are made according to the present invention and areexemplified below. These examples are not meant to limit the presentinvention in any way. The permeability and other calculated parametersfor Examples 1-4 are given below in Table 1. Moreover, Table 1 includesthree comparative examples from prior art publications. The threecomparative examples are not intended to be exhaustive representation ofthe state of the art.

The filter blocks in Examples 1-4 below are made by the followingcompression molding process and equipment. A filter pneumatic press isused which consists of a double-ended vertically mounted cylinder press,a lower piston and an upper piston. The cylinder press bore diameter is2″ (5.1 cm) and the length is 3″ (7.6 cm). The lower piston is driven bya pneumatic cylinder with 1.5″ (3.8 cm) diameter and 3″ (7.6 cm) length(Mosier Fluid Power of Ohio, Miamisburg, Ohio; Model # EJO155A1), andthe upper piston is driven by a pneumatic cylinder with 1.5″ (3.8 cm)diameter and 4″ (10.2 cm) length (Mosier Fluid Power of Ohio,Miamisburg, Ohio; Model # EJO377A3). The upper and lower pistons areheated with heat controllers from Omron Corp. (Schaumburg, Ill.; Model #E5CS) and the cylinder press is heated by a band heater from Fast Heat,Inc. (Elmhurst, Ill.; Model # BW020000). The band heater controller is aVariac from Statco Energy Products, Co., Dayton, Ohio (Model # 3PN1010).

About 42 g of carbon is mixed with about 13.2 g of Microthene®low-density polyethylene (LDPE) FN510-00 binder from Equistar Chemicals,Inc. (Cincinnati, Ohio) and about 4.8 g of Alusil® 70 aluminosilicatepowder from Selecto, Inc. (Norcross, Ga.). Thus, the total carbon mix isabout 60 g. With the upper piston fully retracted and the lower pistonin the fully down position, the cylinder press is filled with the carbonmix and the cylinder press wall is gently tapped to settle the mix. Thecylinder press is back filled to full and struck off to level the mix.The upper piston is slowly lowered, completely engaged to 60 psi (0.41MPa) pressure, and held for a few seconds. Then, the pressure is loweredto near zero and the upper piston is slowly retracted. Again, thecylinder press is filled with more carbon mix, the cylinder wall isgently tapped and struck off to level the mix, the upper piston isslowly lowered to full engagement, and the pressure is raised to 60 psi(0.41 MPa). This procedure is repeated one more time to completely fillthe cylinder press with carbon mix. After the third fill, the 60 psi(0.41 MPa) pressure is maintained on the upper piston. The cylinder heatcontrollers are then turned on and the temperature is set to 400° F.(204° C.). The band heater is also turned on and the Variac controlledis set to 70% or approximately 550° F. (288° C.). The heating cyclelasts for 10 minutes. At the end of the heating cycle the three heatersare turned off, the press is allowed to cool pneumatically forapproximately 10 minutes with air through both the upper and lowerpistons, and the filter is extracted from the cylinder press. Thedimensions of the extracted filters are 2″ (5.1 cm) OD and about 2.5″(6.4 cm) length. Finally, the filters are made radial flow filters bydrilling a central hole, and the outside diameter of the filters isreduced to the final diameter in a lathe.

In all of the Examples below, the liquid used was water, which has aviscosity of 0.01 poise, or 0.01 dynes-s/cm².

EXAMPLE 1

A sample of Nuchar® RGC mesoporous and basic wood-based activated carbonparticles is obtained from MeadWestvaco Corp. (Covington, Va.). Theparticle size distribution of the carbon particles is measured with acommon light scattering method that is known to the art and the resultsare as follows: D_(v,0.50)=33.2 μm, D_(v,0.10)=15.6 μm, D_(v,0.90)=63.4μm, and particle span=1.44. The filter particles are not coated. Theyare mixed with a binder and compression molded to form a radial flowfilter block with the following dimensions: outside radius (r₂)=0.75″(1.9 cm), inside radius (r₁)=0.188″ (0.48 cm), and length=2.3″ (5.8 cm).The filter block volume is 62 cm³ (62 mL), and its face area is 70 cm².To measure the filter block permeability the following conditions areused: flow rate, Q_(r)=625 mL/min (10.4 cm³/s), and pressure drop,ΔP_(r)=18 psi (0.12 MPa, or 1.24*10⁶ dynes/cm²). The permeability of thefilter block is calculated as 3.30×10⁻⁹ cm². The F-VLR of the filterblock is measured according to the method described herein and theresult of that measurement is: 4.3 log reduction in viruses, that is,greater than 99.99% removal of viruses.

EXAMPLE 2

A sample of Nuchar® RGC mesoporous and basic wood-based activated carbonparticles is obtained from MeadWestvaco Corp. The particle sizedistribution of the carbon particles is measured with a common lightscattering method that is known to the art and the results are asfollows: D_(v,0.50)=33.2 μm, D_(v,0.10)=15.6 μm, D_(v,0.90)=63.4 μm, andparticle span=1.44. The carbon particles are coated with polyvinyl amine(PVAm). They are mixed with a binder and compression molded to form aradial flow filter block with the following dimensions: outside radius(r₂)=0.75″ (1.9 cm), inside radius (r₁)=0.188″ (0.48 cm), andlength=2.3″ (5.8 cm). The filter block volume is 62 cm³ (62 mL), and itsface area is 70 cm². To measure permeability the following conditionsare used: flow rate, Q_(r)=940 mL/min (15.7 cm³/s), and pressure drop,ΔP_(r)=15 psi (0.10 MPa, or 1.03*10⁶ dynes/cm²). The permeability of thefilter block is calculated as 5.72×10⁻⁹ cm². The F-VLR of the filterblock is measured according to the method described herein and theresult of that measurement is: 4.0 log reduction in viruses, that is,99.99% removal of viruses.

EXAMPLE 3

A sample of Nuchar® RGC mesoporous and basic wood-based activated carbonparticles is obtained from MeadWestvaco Corp. The carbon particles arefractionated by a common sieving method that is known to the art toobtain the following particle size distribution, which is verified bylight scattering: D_(v,0.50)=48.8 μm, D_(v,0.10)=18.2 μm,D_(v,0.90)=78.2 μm, and particle span=1.23. The carbon particles are notcoated. They are mixed with a binder and compression molded to form aradial flow filter block with the same dimensions, filter block volumeand face area as in Examples 1 and 2. To measure permeability thefollowing conditions are used: flow rate, Q_(r)=625 mL/min (10.4 cm³/s),and pressure drop, ΔP_(r)=12 psi (0.08 MPa, or 0.83*10⁶ dynes/cm²). Thepermeability of the filter block is calculated as 4.75×10⁻⁹ cm². TheF-VLR of the filter block is measured according to the method describedherein and the result of that measurement is: 4.2 log reduction inviruses, that is, greater than 99.99% removal of viruses.

EXAMPLE 4

Two samples of Nuchar® RGC mesoporous and basic wood-based activatedcarbon particles with different particle size distributions are obtainedfrom MeadWestvaco Corp. The two samples are blended together and theresulting particle size distribution is measured by light scattering asfollows: D_(v,0.50)=103.6 μm, D_(v,0.10)=23.8 μm, D_(v,0.90)=233.1 μm,and particle span=2.02. The carbon particles are coated with polyvinylamine (PVAm). They are mixed with a binder and compression molded toform a radial flow filter block with the same dimensions, filter blockvolume and face area as in Examples 1, 2, and 3. To measure permeabilitythe following conditions are used: flow rate, Q_(r)=625 mL/min (10.4cm³/s), and pressure drop, ΔP_(r)=8 psi (0.055 MPa, or 0.55*10⁶dynes/cm²). The permeability of the filter block is calculated as7.13×10⁻⁹ cm². The F-VLR for the resulting block is measured accordingto the method described herein and the result of that measurement is:4.2 log reduction in viruses, that is, greater than 99.99% removal ofviruses.

Table 1 below gives the permeability of the four filter blocksexemplified above and three filter blocks from prior art publications.Additional information about the filter blocks is also given.

TABLE 1 EXAMPLE # 1 2 3 4 5* 6* 7* F-VLR 4.3 4.0 4.2 4.2 4.2 <<3 6Permeability, 3.3 5.72 4.75 7.13 0.73/1.36 1.20 [×10⁻⁹ cm²] Radial Flow?Yes Yes Yes Yes No Yes Yes Filter block 62 62 62 62 58 263 2482 volume,[mL] Outside 3.8 3.8 3.8 3.8 7.6 5.1 12.9 Diameter, [cm] Face Area, 7070 70 70 45.6 405 811 [cm²] Particle 1.44 1.44 1.23 2.02 2.01 Unknown2.8 Span, [−] D_(v,0.50) [μm] 33.2 33.2 48.8 103.6 45 >45 30 *Examplesfrom published patents and applications Example 5 = Example No. 3 fromUS Patent Publication No. 2003/0217963A1 to Mitchell et al. Example 6 =From the Example in U.S. Pat. No. 6,395,190 to Koslow et al. Example 7 =the first Embodiment from US Patent Publication No. 2003/0034290 A1 toTochikubo et al. For Examples 5, 6 and 7 the particle size distributionsare disclosed as weight fractions rather than volume. But those skilledin the art will appreciate that for a sample of one type of particle, aswas the case in each of these three examples, the density of theparticles will be the same and hence the volumetric particle sizedistribution will be the same as the weight based particle sizedistribution. Unknown = these parameters could not be determined fromthe information in the published reference. All blocks in Table 1 werecompression molded except Example 6, which was made by an extrusionprocess. No Metallic biocides were used in any of the examplesVII. Test and Calculation Procedures

The following test procedures are used to calculate the F-VLR and F-BLR.

F-BLR Test Procedure

The filter block to be tested is mounted inside a housing fitted for thefilter block and its flow characteristics (axial, radial, etc.) andwater contaminated with about 1×10⁸ CFU/L E. coli flows through at aflow rate of at least about 600 mL/min. The measurements of the effluentare made after the volumetric flow of liquid through the filter block isequal to at least 10 filter block volumes. The E. coli bacteria used arethe ATCC # 25922 (American Type Culture Collection, Rockville, Md.). TheE. coli assay can be conducted using the membrane filter techniqueaccording to process # 9222 of the 20^(th) edition of the “StandardProcesses for the Examination of Water and Wastewater” published by theAmerican Public Health Association (APHA), Washington, D.C., thesubstance of which is herein incorporated by reference. Other assaysknown in the art can be substituted (e.g. COLILERT®). The limit ofdetection (LOD) is about 1×10² CFU/L when measured by the membranefilter technique, and about 10 CFU/L when measured by the COLILERT®technique. Effluent water is collected after the flow of about the first2,000 filter material pore volumes, assayed to count the E. colibacteria present, and the F-BLR is calculated using the definition.

F-VLR Test Procedure

The housings are the same as those described in the F-BLR procedureabove. Water contaminated with about 1×10⁷ PFU/L MS-2 flows through ahousing/filter system at a flow rate of at least about 600 mL/min. Themeasurements of the effluent are made after the volumetric flow ofliquid through the filter block is equal to at least 10 filter blockvolumes. The MS-2 bacteriophages used are the ATCC # 15597B (AmericanType Culture Collection, Rockville, Md.). The MS-2 assay can beconducted according to the procedure by C. J. Hurst, Appl. Environ.Microbiol., 60(9), 3462 (1994), the substance of which is hereinincorporated by reference. Other assays known in the art can besubstituted. The limit of detection (LOD) is 1×10³ PFU/L. Effluent wateris collected after the flow of about the first 2,000 filter materialpore volumes, assayed to count the MS-2 bacteriophages present, and theF-VLR is calculated using the definition.

The present invention may additionally include information that willcommunicate to the consumer, by words and/or by pictures, that use ofcarbon filter particles and/or filter material of the present inventionwill provide benefits which include removal of microorganisms, and thisinformation may include the claim of superiority over other filterproducts. In a highly desirable variation, the information may includethat use of the invention provides for reduced levels of nano-sizedmicroorganisms. Accordingly, the use of packages in association withinformation that will communicate to the consumer, by words and or bypictures, that use of the invention will provide benefits such aspotable, or more potable water as discussed herein, is important. Theinformation can include, e.g., advertising in all of the usual media, aswell as statements and icons on the package, or the filter itself, toinform the consumer.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference, the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

The embodiments described herein were chosen and described to providethe best illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the invention asdetermined by the appended claims when interpreted in accordance withthe breadth to which they are fairly, legally and equitably entitled.

1. A filter block comprising activated carbon filter particles withoutany metallic biocides, wherein the filter block has permeability ofgreater than about 3.0*10⁻⁹ cm² and a Filter Viruses Log Removal ofgreater than about 2 logs, and wherein the activated carbon filterparticles have a median particle size of less than about 50 μm andhaving a particle span of about 1.4 or less.
 2. The filter block ofclaim 1, wherein the permeability is greater than about 3.5*10⁻⁹ cm². 3.The filter block of claim 1, wherein the Filter Viruses Log Removal isgreater than about 3 logs.
 4. The filter block of claim 1, furthercomprising a binder, wherein the activated carbon filter particles havea median particle size of less than about 40 μm.
 5. The filter block ofclaim 1, wherein the activated carbon filter particles are mesoporousactivated carbon particles.
 6. The filter block of claim 1, wherein atleast a portion of the filter particles are coated with polyvinylamine.7. The filter block of claim 5, wherein the sum of the mesopore and themacropore volumes of said mesoporous activated carbon particles isbetween about 0.2 mL/g and about 2 mL/g.
 8. The filter block of claim 1,wherein the block has a Filter Bacteria Log Removal of greater thanabout 4 logs.
 9. The filter block of claim 1, wherein the block is madeby compression molding.
 10. A filter for providing potable water,comprising: (a) a housing having an inlet and an outlet; (b) a filterblock according to claim 1; and (c) a pressure/flow control device. 11.A kit comprising: i) a filter comprising the filter block according toclaim 1; and ii) a package for containing the filter; and wherein eitherthe package or the filter housing comprises information that the filteror filter material provides: bacterial removal; virus removal; microbialremoval; microorganism removal, killing of bacteria, killing of viruses,killing of microbials, killing of microorganisms, or any combination ofthese.